A known reforming device generates reformed gas, which is a so-called hydrogen rich gas, from a mixture of supplied fuel (e.g., natural gas, liquefied petroleum gas, kerosene, methanol or the like) and steam. The generated reformed gas is supplied to, for example, a fuel electrode of a fuel cell. The fuel cell generates power by use of hydrogen existing in the reformed gas, which is exhaled to he fuel electrode, and oxygen existing in the air, which is exhaled to an air electrode.
A known reforming device includes a reforming portion generating a reformed gas, in which fuel and steam are mixed, and exhausting the reformed gas, a combusting portion generating combustion gas, which is used for heating the reforming portion, a combustion gas channel through which the combustion gas flows, a evaporating portion generating the steam by heating water and supplying the steam to the reforming portion, a carbon monoxide reducing portion reducing the level of carbon monoxide in the reformed gas, which is exhaled by the reforming portion, and supplying the reformed gas to the fuel portion.
According to a hydrogen generating device (reforming device) disclosed in JP2003-252604A, as shown in FIG. 1, a tubular reforming vessel 10 (reforming portion) is installed so as to surround a combustion chamber 17, and a tubular pass 12 flowing a fuel gas on the periphery of the reforming vessel 10 and a tubular evaporating chamber 28 (evaporating portion) on the periphery of the pass 12 flowing the fuel gas are coaxially installed, respectively. The evaporating chamber 28 consists of a first evaporating chamber 18 and a second evaporating chamber 22 installed away from the first evaporating chamber 18 by a partition wall 21. A plurality of open holes 23 is formed on the partition wall 21.
The single tubular cylinder type reforming apparatus (reforming device) disclosed in JP2003-321206A includes an emission tube 14 and a burner 18 (combusting portion). Specifically, the emission tube 14 is positioned inside of circular cases 61 through 66, which are provided perpendicularly, coaxially therewith, the burner 18 is positioned at the upper portion of the emission tube 14. Further, channels are formed between each of the circular cases 61 trough 66, and such channels are filled with a reforming catalyst. The single tubular cylinder type reforming apparatus further includes an outlet channel (combustion gas channel) 80, a channel 50, a CO transformer catalyst layer 10 (a part of a carbon monoxide reducing portion), a water heating channel 34, a heating channel 48, a connecting tube 25 and a CO removal catalyst layer (a part of the carbon monoxide reducing portion) 12. Specifically, combustion gas is inhaled into the outlet channel 80 and exhaled through a heat transmission channel (combustion gas channel) 27, which is formed toward outside of the reforming apparatus, after flowing within outer circumferential portion of the emission tube 14. The channel 50 is formed at an outer circumference of the reforming catalytic layer 8, within which the reforming catalyst is filled, and the channel 50 is connected to the reforming catalytic layer 8 at each lower end portion thereof. The CO transformer catalyst layer 10 is provided at an outer circumference of the channel 50, and the CO transformer catalyst layer 10 is connected to the channel 50 at each upper end portion thereof. The water heating channel 34, provided at an upper circumference of the heat transmission channel 27 at upper portions of the circular cases 61 through 66, heats water by means of the heat emitted from the burner 18. The heating channel 48 is formed at an outer circumference of the CO transformer catalyst layer 10 so as to be connected to an inlet 26 at a lower end of the heating channel 48 and connected to an opening of the reforming catalytic layer 8 at an upper end of the heat channel 48. The water heating channel (evaporating portion)34 is connected to an lower end portion of the heating channel 48 by means of a connecting tube 25. The CO removal catalyst layer 12 is provided at an outer circumference of the water heating channel 34.
According to the hydrogen generating device disclosed in JP2003-252604A, heat is exchanged between a basic ingredient X and water Y flowing within the evaporating chamber (evaporating portion)28; and combustion gas flowing within the combustion gas channel 12 in order to preheat the basic ingredient X and the water Y. However, because the evaporating chamber 28 is positioned at most outer circumference of the device, the heat transmitted to the basic ingredient X and the water Y may be emitted outside of the device through an outer circumferential wall of the evaporating chamber 28. Thus, efficiency of the heat exchange has been decreased.
Further, according to the single tubular cylinder type reforming apparatus disclosed in JP2003-321206A, because the CO removal catalyst layer 12 is provided at an outer circumference of the water heating channel 34, which is provided at an outer circumference of the outlet channel (combustion gas channel) 80, a chance can be reduced of the heat, which is emitted outward from the outlet channel 80, being emitted outward from through the outer circumferential wall of the water heating channel 34. Thus, the heat can be exchanged with appropriate efficiency. However, inside of the outlet channel 80, the heating channel 48 and the CO transformer catalyst layer 10 are provided in that order, the heat emitted inward from the outlet channel 80 is transmitted to the source gas flowing through the heating channel 48, and further transmitted to the CO transformer catalyst layer 10. Thus, because a temperature of the combustion gas cannot be increased to a required temperature, and water flowing within the water heating channel 34 cannot be heated appropriately, it takes some time to start the device, as a result, a level of starting performance may be decreased. In order to increase the level of the starting performance, the level of the combustion load can be increased, or the amount of water supplied to the device can be reduced. However, when the combustion load increased, the efficiency may be decreased, and when the amount of water is reduced, deterioration by carbon deposition on the reforming catalyst, which reaches a high temperature; reduction on a degree of conversion and increment of consistency of carbon monoxide within CO transformer catalyst layer 10 may occur.
Thus, because the heat emitted inward from the outlet channel 80 is transmitted to source gas flowing within he heating channel 48 and further transmitted to the CO transformer catalyst layer 10, a difference of responsibilities exists between the combustion gas and the reformed gas flowing within the CO transformer catalyst layer 10, consequently, heat may be imbalanced when the load is changed, as a result, consistency of the carbon monoxide may be increased due to change of the temperature.
A need thus exists to provide a reforming device that can increase efficiency of the heat exchange by reducing the heat emitted from the evaporating portion in which water is heated by means of the combustion gas, at the same time, even when the load is changed or the environment is changed, the device can stably controls with high robustness.